1. Field of the Invention
The instant invention relates to peristaltic pumps in both design and operation. Peristaltic pumps have advantageous characteristics which cause them to be used widely, especially in the medical field, e.g., blood dialysis. In particular, the invention relates to improvements in peristaltic pumps relating to the loading of said pumps, and the adaptation of those pumps in blood dialysis equipment.
2. Description of the Prior Art and Other Information
Peristaltic pumps, the type wherein the plurality of roller elements move along the inner race of a cylindrical or semi-cylindrical stator casing in order to pump a fluid through a compressible plastic tube, having the requisite resiliency or memory, by means of intermittent compression and expansion reactions generated within the tube are, of course, well known, e.g., U.S. Pat. No. 3,756,752 to Stenner. Great efforts have been made in the art for a number of years in order to improve the simplicity of operation of peristaltic pumps for hospital and laboratory operation in terms of pump efficiency, and finally, of loading of the pumps. It is generally true that most peristaltic pumps in terms of loading require two hands and a fair amoung of brute force in order to get the tubing in place and locked prior to operation of the pump.
For example, the pump disclosed in columns 1 and 2 in FIG. 1 of U.S. Pat. No. 3,791,777 to Papoff et al. comprises a plurality of tubing channels that are adjustable individually for tubing size and plurate. Clearly, they do not open for easy tubing insertion. Likewise, Hogan, U.S. Pat. No. 4,211,519 discloses a peristaltic pump having two identical hingedly connected housing sections; the housing sections require tools to remove and to open the pump for tubing replacement. Moreover, this concept does not allow visual observation of the flow tube. Hein, U.S. Pat. No. 4,239,464 discloses a blood pump comprising an inlet valve, an outlet valve, and a displacement chamber being portions of a common flexible tubing being squeezable between fixed wall and two spaced, movable valve plungers and a displacement plunger arranged on a portion of a tubing therebetween, wherein the valve plungers in the flow direction of the tubing have a dimension exceeding 5 mm, and that in the tubing, with the valve plungers in closed position, a slot is left with a height less than 0.5 mm. The Hein concept applies plate pressure to tubing with quick release to create a vacuum; however, the Hein concept does not contain a rotor or stator for circular occlusion of the flexible tubing.
Lamadrid et al. U.S. Pat. No. 4,256,442 discloses a peristaltic pump including a pivotably mounted pressure plate which, together with a pump roller elements, defines a pump chamber. The mounting system for the pressure plate includes a mechanically-advantaged four-bar linkage arrangement which is said to automatically retain the pressure plate in either its fully open or fully closed position as a result of an over-center type locking construction. In operation, Lamadrid et al. stretches tubing over rotor rollers to provide occlusion pressure. The pivotal member operates very much like a suspender with a belt. A backup pivotal member only comes into play after the tubing becomes stretched sufficiently to provide no tension on the rotor rollers.
Cosentino et al. U.S. Pat. No. 4,363,609 discloses a blood pump system in which a roller pump is provided for pumping blood through a flexible tube. An electrical control circuit is connected to a DC motor having an output shaft for applying the necessary voltage to drive the motor at a predetermined speed. Gearing means are provided connecting the motors' output shaft to drive the roller pump. The pump system of Costenino et al. has a cover which is held in place by the use of two magnets. However, it is also apparent from a review of the '609 patent that the cover is not intended to operate in conjunction with a hinge stator as the tubing is placed on the inside of a specifically confined arcuate bearing surface and two rollers are spring pressed into the tubing. The right side of the Cosentino et al. pump is so configured to act as a tubing retainer that is not pivotal or removable.
Generally speaking, all peristaltic pumps must hold occlusion with one or more rollers until another roller(s) closes the tubing on the next pump stroke. This is preferably done with a "ramp" type of approach to eliminate shock to the pump parts and tubing.
U.S. Pat. No. 4,138,205 to Wallach discloses a peristaltic pump having two stator members pivotably disclosed on diametrically opposite sides of a pump rotor. When in their closed position, the two inside faces of the stator members form an arcuate surface against which the peristaltic tubing rests. To replace the tube, the stator members are first unlocked by turning two hand levers with the stator members, and then swung apart.
Guttmann discloses in U.S. Pat. No. 4,179,249 a quick loading peristaltic pump similar to the one according to the Wallach teaching. The Guttmann pump includes a pair of reaction members pivotably mounted on a base plate for movement between open and closed positions relative to rotor, the reaction members being releasably retained in their closed positions by a locking plate. The compressible tube partially encircles the rotor and has its ends releasably engaged by clamping which prevents axial movement of the tube and is adapted to accommodate tubes of different diameter. Unlike the Wallach pump and its two hand levers, the two pivotal stator members of Guttman are locked in their closed position by means of a swingable locking plate. Wallach and Guttman are typical of the prior art easy loading peristaltic pumps which incorporate two pivotable stator members.
Of lesser interest are the prior art patents to Calvet, U.S. Pat. No. 4,131,399; Grimsrud, U.S. Pat. No. 4,190,536; Savitz et al., U.S. Pat. No. 4,229,299; Hogan, U.S. Pat. No. 4,315,718; Meyer et al., U.S. Pat. No. 4,218,197; and Dellabianca, U.S. Pat. No. 4,060,348. Note also FIG. 1 of U.S. Pat. No. 4,108,575 and the supporting disclosure of Schal. See also recent literature of Sartorius GmbH, P.O. Box 19, D-3400 Gottingen, West Germany, relating to its HEMOPROCESSOR.RTM. easy closing blood pump; and G. A. Carlson et al., "A Portable Insulin Infusion System With a Rotary Cellonoid-Driven Peristaltic Pump", MED. PROGR. TECHNOL. 8 at 49-56 (1980).
Of still lesser interest are Terman et al., U.S. Pat. No. 4,215,668; Tregoning, U.S. Pat. No. 4,319,568; Judson et al., U.S. Pat. No. 3,489,145; Diggins, U.S. Pat. No. 4,333,088; Unger et al., U.S. Pat. No. 3,858,796; Rotta, U.S. Pat. No. 3,862,629; Brumfield, U.S. Pat. No. 3,768,653; Unger et al., U.S. Pat. No. 3,724,747; Bellhouse et al., U.S. Pat. No. 4,328,102; Clemens, U.S. Pat. No. 4,119,046; Hutchisson, U.S. Pat. No. 4,083,777; Cosentino et al., U.S. Pat. No. 4,221,543; Nathan et al., U.S. Pat. No. 4,196,729; Terman et al., U.S. Pat. No. 4,223,672; Xanthopous, U.S. Pat. Des. No. 264,134; and Buckberg et al., U.S. Defensive Publication T 994,001. Note also K. Ayukawa et al., "Stream Lines and Path Lines in a Channel Acting as a Peristaltic Pump", TRANS. (JAPAN) SOC. MECH. ENG. 46 (410b) at 1916-1924 (1980) and C. G. Adem et al., "Variations in Vascular Resistance of Isolated Rat Hearts During Normothermic and Hypothermic Experiments", J. BIOMED. ENG. 3 (2) at 128-133 (April 1981).
3. The Problem
As is demonstrated by the prior art cited above, there has, for quite some time, been a need for a peristaltic pump for the hosiptal and biochemical laboratory which is truly easy loading, i.e., does not require two hands and a large amount of force to get the tubing in place and locked prior to operation. Also, it would be desirable to have the peristaltic pump's rotor available for easy cleaning after periodic use through submersion in cleaning fluids, either by lay persons or hospital personnel. Further, it would be advantageous to minimize the number of moving parts employed in a peristaltic pump, and in particular to minimize absolutely the number of parts, e.g., ball bearings, which must be replaced periodically due to normal pump wear. It would also be desirable to provide a pump in which the fluid moved through the occludable tube could be observed at all times. Finally, it would be most advantageous to provide a pump incorporating only one pivotal stator member.